1. Field of the Invention
The present invention relates to an image heating device for heating an image formed on a recording member by an electromagnetic induction heating system.
2. Description of the Related Art
Recently, in order to comply with demands for energy savings and heating time reduction, an electromagnetic induction heating fixing-device (fuser) has been developed and manufactured for mounting on an image forming apparatus.
In the electromagnetic induction heating system, by passing a high-frequency current through an exciting coil generating a variable magnetic field so as to produce a high-frequency magnetic field, a heating material (conductive member) is heated by an eddy current due to the magnetic field. In the electromagnetic induction heating fixing-device, a fixing material is directly heated using the induction current, so that a higher efficient fixing process is achieved in comparison with a conventional fixing method using a halogen lamp or a ceramic heater.
Recently, in order to prevent an increase in coil temperature due to increased speed, a heating method has also been developed in that the exciting coil is arranged outside the fixing member so as to heat the fixing member from the outside.
In order to reduce the temperature rise time, there is proposed an electromagnetic induction heating fixing-device that uses an endless belt member having a conductive layer as a fixing member, a belt guide member is arranged over substantially the entire internal region of the belt member, and an induction heating unit is arranged outside the belt member so as to heat the belt member from the outside by the electromagnetic induction (see Japanese Patent Laid-Open No. 2003-91186, for example). Also, in order to reduce the temperature rise time, there is proposed an electromagnetic induction heating fixing-device using an endless belt member having a conductive layer as a fixing member and an induction heating unit is arranged outside the belt member so as to heat the belt member from the outside by the electromagnetic induction, a heating roller is arranged inside the belt so as to heat the heating roller by the induction heating unit arranged outside the belt (see Japanese Patent Laid-Open No. 2000-250338, for example).
However, in Japanese Patent Laid-Open No. 2003-91186, since the belt guide member is fixed so as not to rotate, the traveling performance of the belt member is unstable when functioning as the fixing member. Also, since the position opposing the exciting coil flux center corresponding to the maximum exothermic part among opposing parts between the exciting coil and the belt is not in contact with the guide member, the distance between the belt and the coil in the maximum exothermic part varies so as to make the heating of the belt member unstable, resulting in gloss unevenness and fuseing failure due to temperature unevenness within the surface of the belt member. In Japanese Patent Laid-Open No. 2000-250338, since a member for suspending the belt is the rolling roller, the surface of the roller being out of contact with the belt member and not facing the belt member is rotated, so that the heat of the belt is captured by the roller every time the roller comes contact with the belt, resulting in elongation of the temperature rise time.